This invention is concerned generally with universal joints and more particularly with tripod universal joints of the fixed center type. Universal joints of this type are conventionally used in the drive lines of front wheel drive vehicles to transmit torque from the transmission of the vehicle to the front wheels thereof.
A tripod universal joint of the same general type as is under consideration here is disclosed in Futamura et al U.S. Pat. No. 4,421,494. Such a universal joint comprises a housing having a bottom wall and an annular side wall. A spider is located in the housing in spaced relation with the bottom wall and includes a center portion and three angularly spaced trunnions. The trunnions extend radially from the center portion of the spider and are fixed to the side wall of the housing. Each trunnion supports a roller which is adapted to rotate on and slide along the trunnion.
The universal joint further includes a forked shaft having three angularly spaced jaws separated by three angularly spaced slots defining raceways. When the shaft is assembled with the housing and the spider, the rollers of the spider are received in and are adapted to ride along the slotted raceways of the shaft. A centering button with a spherically shaped nose is spring-biased against an inside bearing surface of the forked shaft and causes the universal joint to have a fixed center of angulation.
The universal joint is completed by a retaining clip which has a central base and three angularly spaced spring legs extending axially from the base. The retaining clip is located within the housing near the bottom thereof and its resilient legs are adapted to interlock with the jaws of the shaft in order to hold the shaft and the spider in assembled relation.
After extended wear occurs, it may be necessary to disassemble the universal joint and replace certain ones of its components. In particular, it is frequently necessary to replace the retaining clip, the centering button and the spring or springs which act against the centering button. In cases of extreme wear, it may be necessary to replace the forked shaft.
Once the universal joint has been disassembled for repair, re-assembly of the parts presents a difficult problem. In particular, it is difficult to re-assemble the forked shaft with the spring retaining clip since the dimensional relationships between various components of the joint prevent the shaft from being pushed sufficiently far into the housing to effect a snap interlock between the shaft and the clip.